Predictive Control of Flux Angle for Induction Motors

Abstract

Nowadays, induction motors are widely used in electrical drive systems. Vector control is one of the most utilized methods in these systems. This method has acceptable performance in heavy loading conditions and the rotor flux is the same as the nominal value. However, in light loading, using vector control method results in decreasing the efficiency. When the motor has light loading, there is no need for the nominal flux in order to provide the required torque. Motors are rarely used for operating with their nominal load and the loading is usually different from the nominal value. One of the reasons for this is the overdesign. In this paper, the efficiency of induction motor is improved, especially in light loading. This is accomplished by predictive control of the angle between stator current and rotor flux which is on the d-axis (flux angle). In the proposed method, for light loading condition (the range from no load to a certain value of boundary torque), the flux angle is controlled and kept to a constant value which depends on some of the machine parameters. For the loading range between the boundary torque and the nominal value, the flux angle is controlled but to a variable reference. The designed method can be easily implemented and significantly increases the induction motor efficiency in light loading.